Radial release device

ABSTRACT

A release device having a multi-segment split spool with a central bore adapted to axially restrain a tensioned member. A tensioned tape is overlappingly wound around the spool segments thereby preventing radial movement of the spool segments. The overlapping winding allows for a low profile housing for the-release device. The multiple segments require less radial motion for release of the tensioned member.

CROSS REFERENCES TO RELATED APPLICATIONS

This application is a continuation of, and claims priority to, pendingU.S. Patent Application No. 12/082,818, filed Apr. 14, 2008, which ishereby incorporated by reference herein in its entirety for allpurposes.

BACKGROUND

1. Field of the Invention

The present invention relates to a release device which may to releasesuch items as antennas, solar arrays, positioning mechanisms, and otherdevices.

2. Description of Related Art

A release apparatus, such as a separation spool device, is used torelease a captured member which constrains the deployment of aspacecraft element, such as a solar array and/or reflectors, in thestowed position. In many prior art devices, the spacecraft element wasrestrained with a wire or a holddown rod system which was released usinga pyrotechnic device. Typically, the pyrotechnic device would fire ablade against a base, with the wire or rod to be cut and released.Although useful in many applications, these devices imparted high shockloads into the units which they were to release, as well as thespacecraft itself.

A design that avoided the shocks associated with pyrotechnic releasedevices was the separation spool device, which used a fused element torelease a captured member. U.S. Pat. No. 6,133,818, to Baghdasarian,discusses a release apparatus wherein two piece split spool with anannulus is used to capture a capture member larger in diameter than theannulus of the spool. The two pieces of the split spool are heldtogether with a wire that is wrapped around the spool. A drawback ofthis design is that the wire, wrapped under tension around the outsideof the spool, may have unpredictable dynamics in some cases whenreleased. In some cases, there may be risk of the wire fouling uponitself when released, which may prevent the spool from spreading farenough apart to allow the captured member to pass through, and thus thismay prevent the release device from releasing the stowed spacecraftelement. Another drawback of this design is that a two piece spooldesign presents a geometry that requires significant radial movement ofthe spool pieces to affect the release.

Further, a two segment spool has geometric limitations as far as loadcarrying capacity and a phenomenon referred to as “Friction lock up”condition, a failure to release condition due to friction between thespool-to-captured member interface, and the fact that spherical (ball)end of the captured member leaves the segments contacting the twoextreme points of each segment. These two points are almost 180 degreesapart for a 2-segment spool. A ball end could easily be prevented fromrelease with very little friction between the ball and the spoolinterface.

SUMMARY

A release device having a multi-segment split spool with a central boreadapted to axially restrain a tensioned member. A tensioned tape isoverlappingly wound around the spool segments thereby preventing radialmovement of the spool segments. The overlapping winding allows for alow-profile housing for the release device. Overlapping design of flattape provides predictable unwinding dynamics upon release.

The multiple segments require less radial motion for release of thetensioned member. Further, multiple segments spool reduces the potentialof “Friction lock up” due to smaller contact angle between each segmentwith the captured member (almost 90 for 4-segment, almost 60 for a6-segment, and almost 45 for a 8-segment spool).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a perspective view of portions of a release device accordingto some embodiments of the present invention.

FIG. 1B is a cutaway side view of a release device according to someembodiments of the present invention.

FIG. 2 is a perspective view of portions of a release device accordingto some embodiments of the present invention.

FIGS. 3A-B are views of a two piece spool.

FIGS. 4A-B are views of a six piece spool according to some embodimentsof the present invention.

FIG. 5A is a top view of portions of a release device according to someembodiments of the present invention.

FIG. 5B is a cutaway view of portions of a release device according tosome embodiments of the present invention.

FIG. 6 is a top view of portions of a release device according to someembodiments of the present invention.

FIGS. 7A-B are a partial top view layout and cross-section of a releasedevice illustrating anti-rotation pins according to some embodiments ofthe present invention.

FIG. 8 is a cutaway side view showing an inclined sliding surfaceaccording to some embodiments of the present invention.

FIGS. 9A-B are cutaway side views showing pivoting bases for the spoolsegments according to some embodiments of the present invention.

DETAILED DESCRIPTION

In some embodiments of the present invention, as seen in FIGS. 1A-B, arelease apparatus 10 for controlling the deployment of a desired deviceby releasing a captured member 15 utilizes a multi-piece split spool 11adapted to restrain the captured member 15. The multi-piece spool 11consists of three or more segments 50 which define a central bore 51adapted to restrain a captured member 15. In some embodiments, the spool11 consists of six segments. In some embodiments, the spool consists ofeight segments. As seen in cross-section in FIG. 1A, the segments of thespool are adapted to fittingly receive and axially restrain an expandedportion 18 of the captured member 15 when the segments 50 areconstrained together as a unit. The internal area of the spool 11 in theinterface area of the spool 11 with the expanded portion 18 of thecaptured member 15 may be conical in some embodiments. In someembodiments, the internal area of the spool 11 in this region may be acone or a partial cylinder (or a curved surface other than a cone) withan angle of 30 degrees off of the vertical axis of bore. In someembodiments, the external profile of the expanded portion 18 of thecaptured member 15 may also be conical. In some embodiments, theinterface area may have a curved profile. In some embodiments, theinternal area of the spool may be lubricated with a dry lubricant suchas molybdenum disulfide.

A tensioned tape 12 is wrapped around the external periphery of thespool 11. The tape 12 is adapted to constrain the segment 50 of thespool 11 together. A first end of the tape 12 may be removably fastenedto one of the segments 50 of the spool 11. The fastening of the tape 12to one of the segments provides tangential restraint such that the tapemay be wound under tension around the outer periphery of the spool, andalso will prevent the slipping of the tape around the spool once thistension has been placed in the tape. In some embodiments, the tape 12may be a spring tempered stainless steel which is 0.2 inches wide and0.005 inches thick. Once wound under tension, the second end 13 of thetape 12 may be secured under tension by a fuse wire locking device 14 orother restraint and release system.

Securing the second end 13 of the tape may be done to itself or to anexternal support, not shown in this embodiment.

Segments 50 of spool 11 may be prevented from rotation by use ofanti-rotation pins between each segment, or by other means.

In some embodiments, the tape 12 is wound with its successive layersover each other in plane. This allows for a much more compact overalldesign, in the direction of the axis of the spool, of the release devicecompared to previous designs. Thus, the height of the housing 16 may bekept to a minimum. FIG. 2 illustrates the release apparatus with thetape 12 in relaxed, unwound position. This position is reached after therelease of the second end 13 of the tape 12. Typically, the capturedmember 15 is under tension axially. Thus, with the release of the secondend 13 of the tape 12 and the removal of the constraint on outwardmotion of the spool segments, the axial pull by the captured memberforces the segments of the spool outward in a radial direction. The tape12 has remained in plane and has released and unwound in an orderlyfashion. The segments of the spool 11 are seen in a position furtherfrom the center axis of the constrained spool.

Another advantage of the overlaying tape is that the tape layers havefriction between them, and thus the tension on the tape is reduced inthe radially outward direction with each successive wrap. The tension,therefore, on the release mechanism may be significantly lower than thetension at the center of the tape. Thus, a release device, such as afuse, with a low load capability may be used to release the tape.

FIGS. 3A-B and 4A-B illustrate a contrast between a two segment spoolsystem 30 and a multi-piece spool system 40. The two segment system 30consists of two segments 31, 32 which define a central bore 39. Aninterface surface 33 is adapted to interface with the expanded portionof a restrained member and to restrain its axial motion. The restrainedmember will typically be placed under tension. The tension along theaxis of the bore of the spool will result in both axial and radialloading of the spool segments due to the conical profile of theinterface surface 33 of the spool segments 31, 32. The radial loading ofthe spool segments will be initially be countered by the wound tape asdescribed above. Upon release of tension in the tape, there will nolonger be a constraint on radial motion of the spool segments other thanthe friction of the bases of the spool segments against the adjacentsurfaces. As will be discussed later, friction between surface 33 andexpanded portion of the restrained member (typically a sphericalsurface) will have an effect on separation of spool segments.

The spool segments must move a distance 37 sufficient to allow for theouter diameter 34 of the expanded portion of the restrained member topass through the bore in the axial direction. As the two segments 31, 32begin to separate, the axial force, which in turn drives the separationof the segments, becomes concentrated on the corners 36 of the segments.With just two segments, the force may be concentrated on just fourpoints. With more force concentrated on each point, the possibility ofgalling and sticking at a single point, with a resulting failure torelease the restrained member, is enhanced. In addition, the distance 37that the segments must move is at a maximum.

Referring now to FIGS. 4A-B, a six piece spool system 40 consists of sixspool segments 41, 42, 43, 44, 45, 46. Thus, the interface surface 47 isbroken into six separate pieces. The spool segments must move a distance49 sufficient to allow for the outer diameter 34 of the expanded portionof the restrained member to pass through the bore in the axialdirection. As the segments 41, 42, 43, 44, 45, 46 begin to separate, theaxial force, which in turn drives the separation of the segments, willbe spread across the segments. The distance 49 that the segments 41, 42,43, 44, 45, 46 must travel in order to allow the passage of the expandedportion of the restrained member is significantly less than with a twosegment spool. The differential offset 51 in between the depth of thesegment bore and the diameter of the expanded portion of the restrainedmember in the multi-piece spool system is significantly smaller than thedifferential offset 52 in the two piece spool system. This gives themulti-piece spool the distinct advantage of requiring less radial traveldistance for each segment in order to release the captured member. Theuse of a full circumferential spool reduces the contact forces in theinterface area of the spool segments and the expanded portion of therestrained member.

FIGS. 5A-B illustrate a release system according to some embodiments ofthe present invention. A release apparatus 60 may control the deploymentof a selected device by releasing a captured member 70. A multi-piecesplit spool 67 consists of six segments 74 which define a central bore75. The central bore 75 is sized such that the expanded portion 71 ofthe captured member 70 is constrained from downward axial motion by theinterface portion of the segments 74 of the spool 67.

The segments 74 of the spool 67 are constrained from motion in theexternal radial direction by a wound restraining tape 63. A first end 65of the tape 63 may be constrained from motion along the exterior of thespool by attachment to one of the segments of the spool. A second end ofthe tape 66 may be constrained by a fuse wire release device 69 or othermeans. The housing 61 is low profile due to the use of an overlappingtape as the spool restraint. The housing 61 may include a wall 74adapted to separate the spool and tape from the electrical interfaceportion 68 of the system. The housing 61 may have a circular innerprofile 64 adapted to reduce the likelihood that the tape, as it unwindsand expands radially during the release cycle, will hang up on any innersurfaces. Vertical members 76 may be in place to further separate theinner compartment.

The base 62 is of sufficient strength that it may withstand the axialforce of the captured member. The base 62 may also provide the slidingsurface upon which the spool segments move upon release of the tensionin the tape. The base bore 73 is sized such that the expanded portion 71of the captured member 70 may pass through the base bore upon release.The captured member 70 may be a rod with a threaded interface forconnection into a larger system. As seen in FIG. 5B, the surface 77 uponwhich the spool segments slide in this embodiment is a flat surface, asare the bottoms of the spool segments. The sliding surface and thebottoms of the spool segments may have different geometries is otherembodiments.

FIG. 6 illustrates a release device 80 according to some embodiments ofthe present invention. A tape release lever 82 is mounted within thehousing and rotates around a pin 88. A first end 83 of the tape releaselever 82 includes a tab 89 adapted to hold the wound tape 84 undertension. The tab 89 may be inserted into a hole in the tape. The taperelease lever 82 is adapted to hold the tape using the tab when thelever is in a first position, and to release the tape as the leverrotates to a second position. A second end 81 of the tape release lever82 is adapted to be constrained by a fuse wire release system 86, whichmay be separated from the tape and spool by an interior wall 87. Thesecond end 81 of the tape release lever 82 may be significantly longerthan the first end 83 to allow for the tension of the tape to be heldwith a lower force due to the longer lever arm of the second end 81.

In practice, the tape may be placed under tension by winding the tapearound the spool with the bore in a horizontal position and the tapeextended and under load. In some embodiments of the present invention,as seen in FIGS. 7A-B, a feature may be added to prevent rotation of thespool segments while under the torsional load that may be placed uponthem by the wound tape 107. The spool 100 is seen made up of foursegments 101 in this embodiment. Anti-rotational pins 102 are locatedbetween the segments 101 and are affixed to the base plate 106 of theapparatus. The pins 102 are adapted to prevent rotation of the segments101 yet do not interfere with the outward motion of the segments upontheir release.

The tape may be anchored on a first end in a slot 103 in a spool segment101 adapted to receive the tape 107. The second end of the tape may beanchored to a fuse link 105, which may be attached to an insulator whichis secured to the base plate of the housing in some embodiments.

In some embodiments of the present invention, as seen in FIG. 8, thegeometry of the bottom of the spool segments, and of the surface uponwhich they slide during release, are altered in order to facilitate therelease. The release apparatus 110 may have a spool whose segments 112have an inclined bottom surface 111. An advantage of this inclinedsurface is that the frictional component along the surface is lower thanwould be experienced with a perpendicular sliding surface, such as seenin FIG. 5B. Also, the force 113 in the rod being released has acomponent along the incline, which facilitates the outward motion of thespool segments necessary for release.

In some embodiments of the present invention, as seen in FIGS. 9A and9B, another geometry of the bottom of the spool segments is used. Asseen, the release apparatus 120 uses a pivoting motion as opposed to asliding motion. The spool segments 121 may have a rounded bottom 122which is adapted to pivot within a slot 123 upon release of the tensiondevice constraining the spool. In some embodiments, the bottom of thespool segments may be circular as viewed from the top, in accord withthe external periphery of the segments in the area where the tensiondevice is wound. In some embodiments, the bottom of the spool segmentsmay be linear, such that the pivot lies in a linear slot. In someembodiments, the spool segments may come to a rounded point.

As evident from the above description, a wide variety of embodiments maybe configured from the description given herein and additionaladvantages and modifications will readily occur to those skilled in theart. The invention in its broader aspects is, therefore, not limited tothe specific details and illustrative examples shown and described.Accordingly, departures from such details may be made without departingfrom the spirit or scope of the applicant's general invention.

What is claimed is:
 1. A release apparatus for controlling thedeployment of a device by restraining or releasing a first member undertension in a first direction, which respectively prevents or allows thedeployment of the device, the release apparatus comprising: a pluralityof spool segments, said spool segments adapted to restrain said firstmember along said first direction while said plurality of spool segmentsare in a first constrained position; and a restraining tape wound aroundsaid plurality of spool segments.
 2. The release apparatus of claim 1wherein said restraining tape is wound around said plurality of spoolsegments with overlayed layers.
 3. The release apparatus of claim 2wherein a first end of said restraining tape is releasably attached to arelease device.
 4. The release apparatus of claim 3 wherein a second endof said restraining tape is attached to one of said plurality of spoolsegments.
 5. The release apparatus of claim 3 wherein said first end ofsaid restraining tape is releasably attached to a first portion of saidrestraining tape, and wherein said release device, upon release,releases said first end of said restraining tape from said first portionof said restraining tape.
 6. The release apparatus of claim 3 furthercomprising a housing, and wherein said first end of said restrainingtape is releasably attached to said housing.
 7. The release apparatus ofclaim 3 wherein said release device comprises a pivoting arm, wherein afirst end of said pivoting arm is releasably attached to said first endof said restraining tape, and wherein a second end of said pivoting armis releasably attached to an electrically actuated fuse.
 8. The releaseapparatus of claim 1 wherein said release apparatus further comprises ahousing, and wherein said spool segments contact said housing along acontact surface, said contact surface perpendicular to said firstdirection.
 9. The release apparatus of claim 1 wherein said releaseapparatus further comprises a housing, and wherein said spool segmentscontact said housing along a contact surface, and wherein said contactsurface is sloped downward along said first direction in radialdirection away from the center of said plurality of spool segments. 10.The release apparatus of claim 3 wherein said release apparatus furthercomprises a housing, and wherein said spool segments contact saidhousing along a contact surface, said contact surface is sloped downwardalong said first direction in radial direction away from the center ofsaid plurality of spool segments.
 11. The release apparatus of claim 1wherein said release apparatus further comprises a housing, and whereinsaid spool segments contact said housing along a pivoting contactsurface, and wherein said spool segments are adapted to pivot radiallyoutward from said pivoting contact surface upon release from said firstconstrained position when said first member is under tension along saidfirst direction.
 12. The release apparatus of claim 3 wherein saidrelease apparatus further comprises a housing, and wherein said spoolsegments contact said housing along a pivoting contact surface, andwherein said spool segments are adapted to pivot radially outward fromsaid pivoting contact surface upon release from said first constrainedposition when said first member is under tension along said firstdirection.
 13. A release apparatus for controlling the deployment of adevice by restraining or releasing a first member under tension whichrespectively prevents or allows the deployment of the device, theapparatus comprising: a segmented spool portion, said segmented spoolportion adapted to restrain said first member along a first directionwhile the spool segments are in a first constrained position; and arestraining tape wound around said plurality of spool segments, whereinsaid segmented spool portion consists of three of more segments.
 14. Therelease apparatus of claim 13 wherein said restraining tape is woundaround said segmented spool portion with overlayed layers.
 15. Therelease apparatus of claim 14 wherein a first end of said restrainingtape is releasably attached to a release device.
 16. The releaseapparatus of claim 15 further comprising: a housing; and one or moreanti-rotation pins, said anti-rotation pins affixed to said housingbetween said plurality of spool segments, said anti-rotation pinsadapted to restrict rotary motion of said plurality of spool segmentsrelative to said housing
 17. The release apparatus of claim 15 whereinsaid release apparatus further comprises a housing, and wherein saidspool segments contact said housing along a contact surface, saidcontact surface is sloped downward along said first direction in radialdirection away from the center of said plurality of spool segments. 18.The release apparatus of claim 15 wherein said release apparatus furthercomprises a housing, and wherein said spool segments contact saidhousing along a pivoting contact surface, and wherein said spoolsegments are adapted to pivot radially outward from said pivotingcontact surface upon release from said first constrained position whensaid first member is under tension along said first direction.
 19. Therelease apparatus of claim 15 wherein a second end of said restrainingtape is attached to one of said plurality of spool segments.
 20. Therelease apparatus of claim 15 wherein said first end of said restrainingtape is releasably attached to a first portion of said restraining tape,and wherein said release device, upon release, releases said first endof said restraining tape from said first portion of said restrainingtape.